An intramedullary nail may be implanted in a fractured bone, such as a tibia or a femur, the implantation being such that the nail extends distally and proximally with respect to the fracture, in reinforcement of fractured parts of the bone that have been re-aligned or merely are to be held in alignment for the course of healing repair.
Intramedullary nails of the character indicated are usually prepared with two spaced parallel holes that extend diametrically across the nail near the distal end of the nail and may be prepared with two spaced holes of similar nature, but not necessarily parallel, near the proximal end of the nail. These holes are formed to accept bone screws, and when the nail has been installed, its bone-screw holes are said to be “blind” in terms of the bone-drilling alignment that must be achieved.
The problem has always been one of assuring correct alignment for drilling a hole to accept a bone screw driven through bone for anchoring passage through the intramedullary nail. One of the problems of locating a bone-screw hole in an installed intramedullary nail is the practical fact that the nail may have undergone a slight bend in the course of implantation, so that such holes at the distal end of the nail no-longer have precisely the same location with respect to the proximal end, as was the case prior to nail implantation.
EP 2 049 025 A1 describes a targeting device for targeting a cross bore in a bone nail, the targeting device comprising an arm member coupled to an end portion of the bone nail and an aiming portion forming part of the arm member extending parallel to a longitudinal axis of the bone nail. An adjustable aiming device is mounted on the aiming portion, the adjustable device having a guide bore alignable with the cross bore in the nail. The adjustable device is moveable with respect to the aiming portion in a direction perpendicular to a plane containing both the nail longitudinal axis and central axis of the cross bore. A target indicator is mounted on the adjustable aiming device. Here, the adjustment is performed based on an x-ray image generated when the nail is already inserted into the bone.